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Systematic mutagenesis of the leucine-rich repeat (LRR) domain of CCR4 reveals specific sites for binding to CAF1 and a separate critical role for the LRR in CCR4 deadenylase activity.

CCR4, a poly(A) deadenylase of the exonuclease III family, is a component of the multiprotein CCR4-NOT complex of Saccharomyces cerevisiae that is involved in mRNA degradation. CCR4, unlike all other exonuclease III family members, contains a leucine-rich repeat (LRR) motif through which it makes contact to CAF1 and other factors. The LRR residues important in contacting CAF1 were identified by constructing 29 CCR4 mutations encompassing a majority (47 of 81) of residues interstitial to the conserved structural residues. Two-hybrid and immunoprecipitation data revealed that physical contact between CAF1 and the LRR is blocked by mutation of just two alpha-helix/beta-helix strand loop residues linking the first and second repeats. In contrast, CAF16, a potential ligand of CCR4, was abrogated in its binding to the LRR by mutations in the N terminus of the second beta-strand. The LRR domain was also found to contact the deadenylase domain of CCR4, and deletion of the LRR region completely inhibited CCR4 enzymatic activity. Mutations throughout the beta-sheet surface of the LRR, including those that did not specifically interfere with contacts to CAF1 or CAF16, significantly reduced CCR4 deadenylase activity. These results indicate that the CCR4-LRR, in addition to binding to CAF1, plays an essential role in the CCR4 deadenylation of mRNA.

Pubmed ID: 14734555

Authors

  • Clark LB
  • Viswanathan P
  • Quigley G
  • Chiang YC
  • McMahon JS
  • Yao G
  • Chen J
  • Nelsbach A
  • Denis CL

Journal

The Journal of biological chemistry

Publication Data

April 2, 2004

Associated Grants

  • Agency: NIGMS NIH HHS, Id: 1 F32 GM20235-01
  • Agency: NIGMS NIH HHS, Id: GM41215

Mesh Terms

  • Amino Acid Sequence
  • Enzyme Activation
  • Leucine Zippers
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Proteins
  • RNA, Messenger
  • Ribonucleases
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins